Bottom Line:
Using high-resolution live-imaging data on tagged +TIPs, we show that TACC3 localizes to the extreme microtubule plus end, where it lies distal to the microtubule polymerization marker EB1 and directly overlaps with the microtubule polymerase XMAP215.TACC3 also plays a role in regulating XMAP215 stability and localizing XMAP215 to microtubule plus ends.Taken together, our results implicate TACC3 as a +TIP that functions with XMAP215 to regulate microtubule plus end dynamics.

Mentions:
To gain further insight into how TACC3 mechanistically affects MT plus end behaviors, we examined the subcellular dynamics of TACC3 within living embryonic cells. Thus we tagged full-length TACC3 with GFP and examined its localization within both growth cones and neural crest cells (Figure 3 and Figure 3 Supplemental Movies 1–3). GFP-tagged TACC3 strongly localized to the growing plus ends of MTs in both cell types (Figure 3, A–C and G–I). In growth cones, the mean length of the GFP-TACC3 plus end accumulation was ∼0.70 μm (Figure 3, D and E; data measured from 70 MTs). GFP-TACC3 was primarily detected on MT plus ends that either appeared to be advancing forward or paused, with 100% of growing MTs displaying detectable GFP-TACC3 plus end localization (Figure 3F). Seventy-seven percent of paused MTs still showed GFP-TACC3 localization, whereas 25% of shrinking MTs also had observable GFP-TACC3 localization. These observations were similar in neural crest cells, although the GFP-TACC3 comets were shorter, with a mean length of 0.53 μm (Figure 3, J and K; data measured from 64 MTs). GFP-TACC3 accumulation was detectable on 100% of growing MTs, 69% of paused MTs, and 25% of shrinking MTs (Figure 3L). Thus we find that GFP-TACC3 robustly tracks plus ends of MTs in vertebrate growth cones and neural crest cells.

Mentions:
To gain further insight into how TACC3 mechanistically affects MT plus end behaviors, we examined the subcellular dynamics of TACC3 within living embryonic cells. Thus we tagged full-length TACC3 with GFP and examined its localization within both growth cones and neural crest cells (Figure 3 and Figure 3 Supplemental Movies 1–3). GFP-tagged TACC3 strongly localized to the growing plus ends of MTs in both cell types (Figure 3, A–C and G–I). In growth cones, the mean length of the GFP-TACC3 plus end accumulation was ∼0.70 μm (Figure 3, D and E; data measured from 70 MTs). GFP-TACC3 was primarily detected on MT plus ends that either appeared to be advancing forward or paused, with 100% of growing MTs displaying detectable GFP-TACC3 plus end localization (Figure 3F). Seventy-seven percent of paused MTs still showed GFP-TACC3 localization, whereas 25% of shrinking MTs also had observable GFP-TACC3 localization. These observations were similar in neural crest cells, although the GFP-TACC3 comets were shorter, with a mean length of 0.53 μm (Figure 3, J and K; data measured from 64 MTs). GFP-TACC3 accumulation was detectable on 100% of growing MTs, 69% of paused MTs, and 25% of shrinking MTs (Figure 3L). Thus we find that GFP-TACC3 robustly tracks plus ends of MTs in vertebrate growth cones and neural crest cells.

Bottom Line:
Using high-resolution live-imaging data on tagged +TIPs, we show that TACC3 localizes to the extreme microtubule plus end, where it lies distal to the microtubule polymerization marker EB1 and directly overlaps with the microtubule polymerase XMAP215.TACC3 also plays a role in regulating XMAP215 stability and localizing XMAP215 to microtubule plus ends.Taken together, our results implicate TACC3 as a +TIP that functions with XMAP215 to regulate microtubule plus end dynamics.